What is El Niño and how does it affect weather?

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1. 1

   Current theories on El Niño-Southern Oscillation: A review

   Geofísica Internacional (Sheinbaum)Published Jul 1, 2003Checked Oct 5, 2026

   “Se presenta el estado actual del conocimento sobre la física del fenómeno El Niño-Oscilación del Sur (ENOS). Se describen las principales características basado en observaciones, y se discute la física básica que controla el fenómeno con resultados de modelos de diversa complejidad. ENOS es un fenómeno acoplado del sistema Océano-Atmósfera en el cual los mecanismos de retroalimentación son muy importantes; por lo tanto, es difícil establecer relaciones causales, y a pesar de 20 años de grandes avances en su observación, explicación y predicción, aún quedan preguntas importantes por responder.doi: sin doi”

2. 2

   A Review of Paleo El Niño-Southern Oscillation

   Atmosphere (Lu et al.)Published Mar 30, 2018Checked Oct 5, 2026

   “The Earth has seen El Niño-Southern Oscillation (ENSO)—the leading mode of interannual climate variability—for at least millennia and likely over millions of years. This paper reviews previous studies from perspectives of both paleoclimate proxy data (from traditional sediment records to the latest high-resolution oxygen isotope records) and model simulations (including earlier intermediate models to the latest isotope-enabled coupled models). It summarizes current understanding of ENSO’s past evolution during both interglacial and glacial periods and its response to external climatic forcings such as volcanic, orbital, ice-sheet and greenhouse gas forcings. Due to the intrinsic irregularity of ENSO and its complicated relationship with other climate phenomena, reconstructions and model simulations of ENSO variability are subject to inherent difficulties in interpretations and biases. Resolving these challenges through new data syntheses, new statistical methods, more complex climate model simulations as well as direct model-data comparisons can potentially better constrain uncertainty regarding ENSO’s response to future global warming.”

3. 3

   Changes in El Niño-Southern Oscillation and global frequency entrainment.

   Nature communications (Iwakiri & Kug)Published Jul 1, 2026Checked Oct 5, 2026

   “The El Niño-Southern Oscillation (ENSO) periodicity governs the recurrence of its warm and cold phases, shaping the climate variability and the frequency of extremes, yet remains poorly constrained in climate model projections. Here we assess, using coordinated multi-model large-ensemble simulations, the forced modulation of ENSO periodicity from the last millennium to the future and its global imprint. ENSO periodicity tends to shorten under future warming, and this periodicity shift extends to tropical climate modes and propagates globally through teleconnections, a phenomenon we refer to as ENSO frequency entrainment. The frequency entrainment appears to be ubiquitous, evident in forced responses in last-millennium simulations and under nonstationary, nonmonotonic CO2 forcing, as well as in periodicity modulation driven by internal multi-decadal variability. Changes in future ENSO periodicity may alter the frequency of local climatic events globally, potentially favoring more frequent extreme events.”

4. 4

   ENSO and Climate Change: Reviewing the Literature on The Impact of Global Warming on ENSO and Implications for North America

   Digital Commons - University of South Florida (University of South Florida) (Austin)Published Apr 18, 2023Checked Oct 5, 2026

   “These changes are expected to intensify and redistribute precipitation patterns, increase the frequency of extreme weather events, and alter interactions between ENSO and other climate oscillations. For the United States, projected consequences include heightened drought and aridity in the Southwest, greater variability in agricultural productivity, changes in crop yields linked to ENSO phases, and significant impacts on Atlantic hurricane activity through shifts in atmospheric circulation and wind shear. While uncertainties remain regarding the magnitude and direction of some future ENSO responses, the literature consistently indicates that climate change will amplify many ENSO-related environmental risks, highlighting the need for continued research, improved climate modeling, and adaptive planning to mitigate impacts on ecosystems, agriculture, water resources, and human communities. [austineva_...ough Draft | PDF]”

5. 5

   A Review of Atmosphere–Ocean Forcings Outside the Tropical Pacific on the El Niño–Southern Oscillation Occurrence

   Atmosphere (Chen et al.)Published Nov 12, 2018Checked Oct 5, 2026

   “This paper reviews the impacts of the atmosphere–ocean variability outside the tropical Pacific on the ENSO variability, as well as their associated physical processes. The review begins with the contribution of the atmosphere–ocean forcings over the extratropical North Pacific, Atlantic, and Indian Ocean on the ENSO occurrence. Then, an overview of the extratropical atmospheric forcings over the Northern Hemisphere (including the Arctic Oscillation and the Asian monsoon systems) and the Southern Hemisphere (including the Antarctic Oscillation and the Pacific–South American teleconnection), on the ENSO occurrence, is presented. It is shown that the westerly (easterly) wind anomaly over the tropical western Pacific is essential for the occurrence of an El Niño (a La Niña) event. The wind anomalies over the tropical western Pacific also play a key role in relaying the impacts of the atmosphere–ocean forcings outside the tropical Pacific on the ENSO variability. Finally, some relevant questions, that remain to be explored, are discussed.”

6. 6

   A review of the El Niño Southern Oscillation impacts on Australian climate

   Research paper (Taschetto et al.)Published Mar 14, 2026Checked Oct 5, 2026

   “We will discuss the links between ENSO diversity, weather patterns, and associated extreme events, such as droughts and floods.In a warmer climate, the ENSO-Australian rainfall relationship is projected to intensify by about 10-20%, consistent with many other regions across the globe. ENSO-driven precipitation and surface temperature variability is projected to strengthen in September to November over southeastern and southern Australia, while the largest changes are projected to occur during the warm season from December to February over most of western and northern Australia.Despite considerable improvements in ENSO predictability and seasonal outlooks over the past four decades, predicting its impacts remains challenging because of large internal atmospheric variability. In addition, the observed cooling trend in the Pacific Ocean directly challenges the accuracy of El Niño-like warming projections in a future warming climate. These evolving ENSO features highlight the need for strategic research, sustained in situ monitoring, reduced model biases, and improved understanding of the anthropogenically induced changes in Pacific temperatures to support adaptation strategies.”

7. 7

   Review article. Studying climate effects on ecology through the use of climate indices: the North Atlantic Oscillation, El Niño Southern Oscillation and beyond

   Proceedings of the Royal Society B Biological Sciences (Stenseth et al.)Published Oct 7, 2003Checked Oct 5, 2026

   “Several other large-scale climate patterns also exist. Although less well known outside the field of climatology, these patterns are also likely to be of ecological interest. We provide an overview of these climate patterns within the context of the ecological effects of climate variability. The application of climate indices by definition reduces complex space and time variability into simple measures, 'packages of weather'. The disadvantages of using global climate indices are all related to the fact that another level of problems are added to the ecology-climate interface, namely the link between global climate indices and local climate. We identify issues related to: (i) spatial variation; (ii) seasonality; (iii) non-stationarity; (iv) nonlinearity; and (v) lack of correlation in the relationship between global and local climate. The main advantages of using global climate indices are: (i) biological effects may be related more strongly to global indices than to any single local climate variable; (ii) it helps to avoid problems of model selection; (iii) it opens the possibility for ecologists to make predictions; and (iv) they are typically readily available on Internet.”